If you've used a PC basically ever in your life, you know that holding down the Ctrl+Alt+Del keys is a pretty fundamental command that either reboots your computer, launches the Task Manager or, in some versions of Windows, lets you log on.

I've been using PCs since I was a kid. Ctrl+Alt+Del is as engrained in me as is looking both ways before crossing a street or putting on my shoes before I leave the house.

But Microsoft co-founder and tech genius Bill Gates now thinks the three-button command was a mistake. It should have been simpler.

"So we could have had a single button, but the guy who did the IBM keyboard design didn't want to give us our single button," Gates said recently at a Harvard fundraising event. "So we had, we programmed at a low level -- it was a mistake."

That guy was David Bradley, an engineer who worked on the original IBM computer. Apparently the initial logic to requiring three buttons was so that users didn't accidentally reboot their PCs. Mistake or not, the function has lived on through many iterations of Windows.

But since Gates has us thinking about Microsoft's mistakes, let's take a quick look at how the tech giant has managed to mess up over the years. (Ctrl+Alt+Del doesn't even register on our radar.)

1. Windows Vista
When you think of "Microsoft" and "disaster," Windows Vista almost always is the first thing that comes to mind. Released in 2007, the operating system was scoured by bad reviews, with people complaining that it was slow, that apps didn't work, that it had poor driver support and was overpriced. And, in the public court of opinion, Vista simply paled in comparison to Windows XP. Outgoing chief executive Steve Ballmer even said recently that Vista is among his biggest regrets.

2. Mobile
Apparently Microsoft was so focused on Vista that it forgot to take advantage of the now-exploding mobile market. Sure, Microsoft has smartphones and tablets, but can we say ... Apple? Android? Microsoft ranks third in this market when it had an opportunity to be the leader. This also is among Ballmer's biggest regrets as chief executive. Let's not forget that he LAUGHED when Apple first released the iPhone.

"I regret there was a period in the early 2000s when we were so focused on what we had to do around Windows [Vista] that we weren't able to redeploy talent to the new device called the phone," he said during a recent call with analysts.

Last year, Microsoft reported a $6.2 billion write-down related to its 2007 acquisition of digital marketing company aQuantive. At the time, it was thought that aQuantive would help fuel Microsoft's online advertising war with Google and Yahoo. I guess that didn't work out so well.

This by no means is an exhaustive list. Feel free to add any other mistakes that come to mind in the comments below.